U.S. patent number 8,662,069 [Application Number 11/992,694] was granted by the patent office on 2014-03-04 for cooking top with gas burner comprising a semi-permeable element.
This patent grant is currently assigned to Indesit Company S.P.A.. The grantee listed for this patent is Silvio Corrias, Luisa d'Alessandro, Alberto Gasparini, Paolo Santonicola. Invention is credited to Silvio Corrias, Luisa d'Alessandro, Alberto Gasparini, Paolo Santonicola.
United States Patent |
8,662,069 |
Gasparini , et al. |
March 4, 2014 |
**Please see images for:
( Certificate of Correction ) ** |
Cooking top with gas burner comprising a semi-permeable element
Abstract
The present invention relates to a cooking top (1), in
particular adapted to be used in a household environment,
comprising at least one gas burner (40) which can be used with at
least one fuel gas. The cooking top also comprises flame divider
means (9) associated with the gas burner (40) and comprising at
least one semi-permeable element (90), which is permeable to
gaseous substances and substantially impermeable to liquid
substances. The semi-permeable element (90) may be a
micro-perforated sheet, a fibrous membrane, or a porous
membrane.
Inventors: |
Gasparini; Alberto (Fabriano,
IT), Corrias; Silvio (Moncalvo, IT),
d'Alessandro; Luisa (Scanno, IT), Santonicola;
Paolo (Fabriano, IT) |
Applicant: |
Name |
City |
State |
Country |
Type |
Gasparini; Alberto
Corrias; Silvio
d'Alessandro; Luisa
Santonicola; Paolo |
Fabriano
Moncalvo
Scanno
Fabriano |
N/A
N/A
N/A
N/A |
IT
IT
IT
IT |
|
|
Assignee: |
Indesit Company S.P.A.
(Fabriano, IT)
|
Family
ID: |
37745599 |
Appl.
No.: |
11/992,694 |
Filed: |
July 28, 2006 |
PCT
Filed: |
July 28, 2006 |
PCT No.: |
PCT/IB2006/002073 |
371(c)(1),(2),(4) Date: |
March 27, 2008 |
PCT
Pub. No.: |
WO2007/036772 |
PCT
Pub. Date: |
April 05, 2007 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20090277439 A1 |
Nov 12, 2009 |
|
Foreign Application Priority Data
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|
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|
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Sep 30, 2005 [IT] |
|
|
TO2005A0685 |
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Current U.S.
Class: |
126/39H; 126/39K;
126/39J |
Current CPC
Class: |
F24C
3/085 (20130101); F23D 14/08 (20130101); F23D
2203/105 (20130101); F23D 2203/103 (20130101); F23D
2212/201 (20130101); F23D 2203/102 (20130101); F23D
2212/103 (20130101) |
Current International
Class: |
F24C
3/02 (20060101) |
Field of
Search: |
;431/329,328
;126/39J,43-49,39H |
References Cited
[Referenced By]
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Other References
US. Appl. No. 12/528,371, filed Aug. 26, 2009 by Tiziano Lacche'
entitled Gas Burner System for Food Cooking Appliances, 15 pages.
cited by applicant .
U.S. Appl. No. 12/571,489, filed Oct. 1, 2009 by Paolo Faraldi,
entitled Protective Liner and System for Protecting a Cooking Top,
21 Pages. cited by applicant.
|
Primary Examiner: Rinehart; Kenneth
Assistant Examiner: Pereiro; Jorge
Attorney, Agent or Firm: Cesari and McKenna, LLP
Claims
The invention claimed is:
1. A cooking top comprising: at least one burner for use with at
least one fuel gas; each gas burner having: first means including
an injector adapted to supply said fuel gas or a mixture thereof
with air; second means including a Venturi element adapted to draw
the air; third means adapted to mix and/or provide combustion of
the fuel gas and the air supplied by said first and second means;
and flame divider means secured to said gas burner, said flame
divider means including at least one semi-permeable element having
a substantially annular shape, said semi-permeable element being a
micro-perforated sheet that is permeable to gaseous substances, in
particular to said fuel gas and to any mixture including said fuel
gas and the air, and being substantially impermeable to liquid
substances, wherein holes on the semi-permeable element are more
densely distributed in a peripheral area than in a central area,
and wherein the flame divider means allows a flame generated by the
combustion of the fuel gas and the air to exit through the
semi-permeable element.
2. The cooking top according to claim 1, further comprising: a
covering element; and said third means is a burner cup having a
substantially axially symmetric shape, the axis being preferably
essentially orthogonal to the covering element.
3. The cooking top according to claim 2, wherein said flame divider
means are connected to one or both of said at least one burner and
the covering element.
4. The cooking top according to claim 2, wherein one or both of
said flame divider means and said semi-permeable element have a
substantially hollow cylindrical shape with an axis preferably
coinciding with the axis of said third means; and said gas burner
and said semi-permeable element can generate a crown flame, said
crown flame being a flame which propagates in a substantially
tangential direction relative to the circumference of the flame
divider.
5. The cooking top according to claim 1, wherein said
semi-permeable element is positioned on top of said third
means.
6. The cooking top accordingly to claim 5, wherein one or both of
said flame divider means and said semi-permeable element have a
substantially axially symmetric shape with an axis that essentially
coincides with the axis of said third means.
7. The cooking top according to claim 1, further comprising a
covering element; and one or both of said flame divider means and
said semi-permeable element are located essentially at the same
level relative to the covering element.
8. The cooking top according to claim 7 further comprising pot
supporting means, said pot supporting means reaching a height being
equal to or lower than 30 mm above said covering element.
9. The cooking top according to claim 8, wherein said pot
supporting means reaches a height between 15 mm and 20 mm above
said covering element.
10. The cooking top according to claim 1, wherein said gas burner
and said semi-permeable element can generate a carpet flame, said
carpet flame being a flame which propagates in a substantially
orthogonal direction relative to a covering element.
11. The cooking top according to claim 1, wherein said Venturi
element is horizontal.
12. The cooking top according to claim 1 further comprising said
semi-permeable element and said flame divider means being located
at the same level above a visible surface of the cooking top.
13. The cooking top according to claim 1 wherein the flame divider
means further includes a central portion that is not
micro-perforated.
14. The cooking top according to claim 13 wherein the central
portion is a hole.
15. A cooking top comprising: at least one gas burner which can be
used with at least one fuel gas, each gas burner having: (i) first
means adapted to supply the fuel gas or a mixture thereof with air;
(ii) second means adapted to draw the air; and (iii) third means
adapted to supply the fuel gas or a mixture thereof with the air;
flame divider means associated with said gas burner, said flame
divider means having at least one semi-permeable element having a
substantially annular shape, said semi-permeable element being a
micro-perforated sheet that is permeable to gaseous substances, in
particular to said fuel gas and to any mixture including said fuel
gas and the air, and being substantially impermeable to liquid
substances; wherein holes on the semi-permeable element are more
densely distributed in a peripheral area than in a central area;
wherein said flame divider means allows a flame generated by a
combustion of the fuel gas and the air to exit through the
semi-permeable element; wherein said flame divider means is secured
to one or both of said gas burner and a covering element; wherein
said third means is a burner cup having a substantially axially
symmetric shape, an axis being preferably essentially orthogonal to
the covering element; and at least one securing device adapted to
connect said flame divider means to one or both of said covering
element and said gas burner.
16. The cooking top according to claim 15, wherein said flame
divider means includes a housing means adapted to house said at
least one securing device; said third means includes a supporting
means; wherein said housing means includes a hole that is coaxial
to said semi-permeable element; said securing device includes a
first part being substantially discoidal in shape and a second part
being substantially tubular in shape; and a connection of said
flame divider means to one or both of said cooking top and said at
least one gas burner being provided through interposition of a
portion of said flame divider means between said supporting means
and said first part of said securing device.
17. A cooking top comprising: at least one gas burner which can be
used with at least one fuel gas; flame divider means associated
with said at least one gas burner, said flame divider means
including at least one semi-permeable element having a
substantially annular shape, said semi-permeable element being a
micro-perforated sheet that is permeable to gaseous substances
including said fuel gas and to any mixture including said fuel gas
and air, and being substantially impermeable to liquid substances,
wherein said flame divider means allows a flame generated by a
combustion of the fuel gas and the air to exit through the
semi-permeable element; wherein said flame divider means includes
housing means adapted to house at least one securing device, said
at least one securing device having a first part being
substantially discoidal in shape and a second part being
substantially tubular in shape, said housing means having an
opening that is coaxial to said semi-permeable element; a
connection of said flame divider means to one or both of said
cooking top and said at least one gas burner being provided through
interposition of a portion of said flame divider means between a
supporting means and said first part of said securing device; and
wherein said securing device further includes flow diverter means,
said flow diverter means consisting of one or both of a flared
surface and a gradually decreasing section of said second part of
said securing device.
18. The cooking top according to claim 17, wherein said securing
device is a removable device adapted to grant access inside the gas
burner for maintaining said gas burner and to allow one or both of
said flame divider means and said semi-permeable element to be
removed.
19. A cooking top comprising: at least one gas burner for use with
at least one fuel gas; first means including an injector adapted to
supply said fuel gas or a mixture thereof with air; second means
including a Venturi element; third means adapted to mix and/or
provide combustion of includes fuel gas and includes air supplied
by said first and second means; flame divider means associated with
said at least one gas burner, said flame divider means including at
least one semi-permeable element having a substantially annular
shape, said semi-permeable element being a micro-perforated sheet
that is permeable to gaseous substances, including the fuel gas and
a mixture including said fuel gas and the air, and being
substantially impermeable to liquid substances, wherein the flame
divider means allows a flame generated by the combustion of the
fuel gas and the air to exit through the semi-permeable element;
diverter means adapted to divert any liquid substances coming from
said semi-permeable element toward areas wherein said liquid
substances cannot hinder the operation of said gas burner, said
diverter means consisting of die-cast or forged profiles made of
sheet-metal, brass, cast-iron or steel having perforations adapted
to allow gaseous substances to flow through to supply said gas
burner and having a diameter adapted to prevent said flow from
suffering high load losses.
Description
The present invention relates to a cooking top, in particular
adapted to be used in a household environment, comprising at least
one gas burner.
At present, several typologies of cooking tops adapted to be used
in a household environment are available on the market, the most
widespread typology using one or more gas burners, wherein the
amount of heat necessary for cooking food is generated through
combustion of a gas appropriately mixed with air. Many gas burners
currently installed in cooking tops for domestic use comprise two
external components: a flame divider and a cap. The flame divider
is usually made of die-cast aluminium and is adapted to generate a
flame having a crown configuration, whereas the cap, usually made
of enamelled cast iron (or brass alloy, or steel), acts as a flame
divider closing element, thus preventing the air-gas mixture from
flowing axially out of the burner. The assembly consisting of flame
divider and cap originates a so-called "cup" burner using, as
primary air to be mixed with gas, the air being present above the
cooking top, which enters the burner through access areas delimited
by so-called "skirts", i.e. profiles suitably applied to the
underside of the flame divider.
By "crown flame" it is meant a flame having a substantially radial
propagation direction. If emitted at an insufficient height above
the cooking top, it may cause a low-O.sub.2 combustion resulting in
the generation of a high level of unburnt products (CO and
NO.sub.x) and, due to the thermal content of the flame, it may lead
to deformation and/or blackening of the portion of the cooking top
surrounding the burner. In order to obtain an adequate primary air
flow toward the gas mixing area and to have such an amount of
secondary air available as to obtain a low-CO and low-NO.sub.x
combustion, the cup burner must reach a certain height above the
cooking top wherein it is installed, and the pot supports must
remain at a suitable height (between 15 and 20 mm) relative to the
burner. In particular, the height of the cup burner is
approximately 30 mm above the cooking top, so that it is necessary
that the pot supports used on the cooking top reach a height of
approximately 45/50 mm above the cooking top.
Though the above-mentioned gas burners offer a number of advantages
which promoted their large-scale diffusion, such as adaptability to
different types of fuel gas and competitive industrial costs, they
remain however very difficult to clean. As a matter of fact, many
gas burners for domestic use currently available on the market
require the removal of external components to be cleaned properly.
Once cleaned separately, said external components must then be
repositioned correctly in order to reassemble the gas burner. It
follows that cleaning cooking tops available on the market today
requires much time and generally gives bad results, also because of
the very complex geometry of said external components, which
hinders dirt removal.
The general object of the present invention is to provide an
improved cooking top compared to the prior art.
It is a specific object of the present invention to overcome the
above drawback through a cooking top with at least one innovative
gas burner adapted to be preferably installed in a household
environment.
The cooking top adapted to substantially attain said objects
incorporates the features set out in the annexed claims, which form
an integral part of the present description.
The present invention is based on the idea of providing a cooking
top which, to be cleaned, does not require the removal of any
external components or, as an alternative, only requires a minimal
removal of external components, so as to offer the users of the
cooking top according to the present invention a substantial time
saving and a considerable increase in the effectiveness of the
cleaning treatment.
According to the present invention, said idea is implemented
through a gas burner comprising a semi-permeable element (typically
micro-perforated sheet or fibrous membrane or porous membrane)
capable of withstanding high temperatures such as those generated
by the combustion of a fuel gas and air; said semi-permeable
element is permeable to fuel gas and to any mixture comprising fuel
gas and air, and is substantially impermeable to liquids.
By "semi-permeable" element it is meant, in the present description
and in the annexed claims, an element which can be run through by
flows of gaseous substances, such as an air-gas mixture, at the
same time being capable of rejecting, totally or almost totally,
any flow of liquid substances. In the event that liquid flows
should manage to run through it, the semi-permeable element is
advantageously capable of ensuring that said liquid flows do not
compromise the correct functionality of the gas burner, i.e. it is
capable of ensuring that the gas burner can be lighted again should
said liquid flows extinguish the flame.
By "substantially impermeable to liquids" it is meant, in the
present description and in the annexed claims, an element which is
capable of preventing, totally or almost totally, any liquids to
flow through. In the event that liquid flows should manage to run
through it, said element is advantageously capable of ensuring that
said liquid flows do not compromise the correct functionality of
the gas burner, i.e. it is capable of ensuring that the gas burner
can be lighted again should said liquid flows extinguish the
flame.
The semi-permeable element may typically be a micro-perforated
sheet, or a fibrous membrane, in particular made of metal, metal
alloy, ceramic or carbon fibers, or a porous membrane, in
particular made of a ceramic material, a composite material or a
metal material.
The present invention will become apparent, together with its
further advantages, from the following detailed description and
from the annexed drawings, which are supplied by way of
non-limiting example, wherein:
FIG. 1 schematically shows a detail of a cooking top which
represents a possible embodiment of the present invention;
FIGS. 2A and 2B are schematic sectional views of a cooking top
which represents a possible embodiment of the present
invention;
and
FIGS. 3a-3d schematically shows a possible embodiment of a
component of a cooking top 1 according to the present invention, in
particular of the component called "flame divider means".
FIG. 1 illustrates a cooking top 1 according to the present
invention, in particular a flush-mountable cooking top 1. The
cooking top is so shaped as to comprise a box 7 closed on top by a
covering element, specifically a substantially flat visible surface
30, on which a plurality of housing means is obtained, at least one
of said housing means being preferably a hole adapted to
accommodate a burner, in particular a gas burner 40 as shown in the
sectional views of FIGS. 2A and 2B. The cooking top may also
comprise pot supporting means 6, adapted to ensure an appropriate
separation distance between the visible surface 30 of the cooking
top 1 and a pot containing food to be cooked, as well as interface
means 27 adapted to, among other things, allow to adjust and/or
display the operating parameters of each burner. The interface
means 27 shown in FIG. 1 consist of a "touch control" interface,
but they may also consist of a mechanical interface with on-off
taps. The gas burner 40 illustrated in FIGS. 2A and 2B, adapted to
be installed in a cooking top 1 according to the present invention,
comprises first means adapted to supply fuel gas to the gas burner
and preferably comprising an injector 11, second means adapted to
draw air inside the gas burner and preferably comprising a Venturi
element 10, and third means adapted to mix fuel gas with air and/or
to provide the combustion of fuel gas and/or any mixture comprising
fuel gas and air, and preferably comprising a burner cup 20.
More in detail: the first means operate as gas injection means and
comprise in particular the injector 11 (which may be either
vertical, i.e. with its axis parallel to the axis of the burner cup
20, or horizontal, i.e. with its axis orthogonal to the axis of the
burner cup 20), adapted to spread the gas inside the gas burner 40,
and the injector holder 12, adapted to connect the injector 11 to
the gas supply main; the second means operate as means for drawing
primary air inside the gas burner 40 and as air-gas mixing means,
and comprise in particular the intakes 18A-18N, adapted to allow
primary air to flow inside the gas burner 40, and the Venturi
element 10 (which may be either vertical, i.e. with its axis
parallel to the axis of the burner cup 20, or horizontal, i.e. with
its axis orthogonal to the axis of the burner cup 20, and which in
FIGS. 2A and 2B is connected to the burner cup 20 to the plate 15
through the plate 15), adapted to create, inside the gas burner 40,
a vacuum adapted to convey gas and primary air toward the mixing
and/or combustion area and the third means operate as structural
means and advantageously have a substantially axially symmetric
shape, with an axis essentially orthogonal to the visible surface
30 of the cooking top 1, and comprise in particular the burner cup
20, which is adapted to ensure a stable support for the other
burner components on top of it and to delimit the area where the
mixing of gas and primary air and/or the combustion of the air-gas
mixture takes place.
It is now worth specifying the meaning of the terms "primary air"
and "secondary air" as used in the present description. "Primary
air" is air mixed with fuel gas inside the gas burner 40, whereas
"secondary air" is air added to the already formed air-gas mixture
in the area outside the cooking top 1 surrounding the gas burner
40, which air provides the additional O.sub.2 required for a proper
combustion. According to an advantageous embodiment of the cooking
top 1 according to the present invention, the intakes 18A-18N for
primary air access are obtained directly on the burner cup 20,
specifically on the portion thereof being adjacent to the injector
11 and upstream of the Venturi element 10. In order to ensure a
stoichiometrically correct mixture of gas and primary air in
accordance with the combustion process the mixture will be
subjected to, the intakes 18A-18N obtained on the burner cup 20 are
large enough to provide an adequate primary air flow through them.
In the event that natural circulation does not guarantee a
sufficient primary air flow rate to properly supply air to the gas
burner 40, a primary air forced circulation system may be
associated with the gas burner 40.
The terms "crown flame" and "carpet flame" will also be used in the
present description. A "crown flame" is a flame which propagates
out of the gas burner 40 in a substantially radial direction
relative to the axis of the gas burner 40, i.e. in a substantially
tangential direction relative to the visible surface 30 of the
cooking top 1. Some examples of crown flames are all those flames
generated by gas burners comprising, as external components, a
flame divider and a cap such as those known in the art. A "carpet
flame", on the other hand, is a flame which propagates out of the
gas burner 40 in a substantially axial direction relative to the
axis of the gas burner 40, i.e. in a substantially orthogonal
direction relative to the visible surface 30 of the cooking top 1.
A carpet flame may be either a "total" carpet flame or a
"perimetric" carpet flame, depending on whether it covers a
geometric figure (generally a circle) entirely or it covers just
the peripheral portion of said geometric figure (generally a
circular crown).
The flame divider means 9 may be connected to the visible surface
30 and/or to the burner 40; furthermore, they comprise at least one
semi-permeable element 90, being permeable to fuel gas and to any
mixture comprising fuel gas and air and being substantially
impermeable to liquids, which may be a micro-perforated sheet, or a
fibrous membrane made of metal, metal alloy, ceramic or carbon
fibers, or a porous membrane made of a ceramic, composite or metal
material. The semi-permeable element 90 is located on top of the
third means of the gas burner 40, in particular on top of the
burner cup 20. Advantageously, the flame divider means 9 and/or the
semi-permeable element 90 have a substantially axially symmetric
shape, the axis of the flame divider means 9 and/or of the
semi-permeable element 90 preferably essentially coinciding with
the axis of the third means of the gas burner 40. The flame divider
means 9 also provide the functions of delimiting the internal
environment of the gas burner 40 at the top and of allowing the
flame generated by the combustion of the air-gas mixture to exit
the gas burner 40 through the semi-permeable element 90.
The semi-permeable element 90 may be required to have a number of
specific properties, including: permeability to a gas and to
air-gas mixtures, said gas being preferably a natural fuel gas such
as CH.sub.4, or a liquefied fuel gas like LPG, or an artificial
fuel gas like the so-called "town gas", obtained through
gasification of liquid or solid fuels, or any other fuel among
those used in the different countries; total or essentially total
impermeability to liquid substances, which cannot prevent the
ignition of the gas burner 40 even when overflowing from a
container having a certain height (which can be assumed to be 250
mm); appropriate porosity to ensure the above-described
semi-permeability and at the same time to cause low load losses to
the flows of gas or air-gas mixtures going through the
semi-permeable element 90, so that they can flow out of the gas
burner 40 at an adequate velocity to ensure flame stability during
the combustion (e.g. for air-CH.sub.4 mixtures, said velocity is
preferably comprised between 1.5 m/s and 3 m/s); high thermal
resistance, which prevents the semi-permeable element 90 from
suffering evident deformation when run through by the flame;
sufficient mechanical strength to prevent the semi-permeable
element 90 from suffering evident deformation should it undergo an
accidental impact, e.g. against a cooking container, or should it
fall down during maintenance operations, and to prevent it from
suffering evident abrasion during cleaning operations; sufficient
thermomechanical strength to ensure that any deformation suffered
by the semi-permeable element 90 should it come in contact with an
overflowing liquid having a different temperature is minimal and/or
adequate surface finish to properly integrate said semi-permeable
element 90 in or with the flame divider means 9 and with the
cooking top I whereon the burner is installed, without evident
blackening of said semi-permeable element 90 during the operation
of the gas burner 40.
According to a first possible embodiment of the present invention,
the flame divider means 9 comprise a sheet, in particular a metal
or metal alloy sheet, which is characterized by being
micro-perforated, i.e. by comprising a series of holes whose
diameter is preferably equal to or smaller than the sheet
thickness. The holes and the surrounding sheet form as a whole the
semi-permeable element 90. FIGS. 3A and 3B show, for the purpose of
explaining said first embodiment of the present invention, an
example of a micro-perforated sheet comprised in flame divider
means 9 (which can be used with the gas burner 40 shown in FIGS. 2A
and 2B) and adapted to be used as a semi-permeable element 90.
Furthermore, the enlargement annexed to FIG. 3A shows a detail of
said micro-perforated sheet to illustrate a possible distribution
of the holes in the semi-permeable element 90. The thickness of the
micro-perforated sheet is preferably about 1 mm, so as to obtain a
valid compromise between the mechanical strength of the
micro-perforated sheet and the load losses undergone by the air-gas
mixture flowing through the micro-perforated sheet. If the
thickness is approximately 1 mm, the diameter of the holes of the
micro-perforated sheet will be advantageously comprised between 100
.mu.m and 1 mm.
According to a second possible embodiment of the present invention,
the flame divider means 9 comprise, as a semi-permeable element 90,
a fibrous membrane made of e.g. metal, metal alloy, ceramic or
carbon fibers, or a porous membrane made of e.g. a ceramic,
composite or metal material, both of said membranes being able to
ensure semi-permeability as well as an adequate gaseous flow and
adequate thermal, mechanical and thermomechanical resistance. In
particular, the most suitable membranes to be used in the cooking
top 1 according to the present invention are membranes made out of
woven, unwoven or partially woven metal fibers specifically
designed for use near heat sources.
Many examples of the above metal fiber membranes can be found in
the patent literature: by way of example and not by way of
limitation, it can be stated that the most suitable membranes to be
used in the cooking top I according to the present invention are
those described in patent applications WO94/14608, WO95/27871 and
WO02/99173.
In the present description a cooking top 1 according to the present
invention will be illustrated in detail, which comprises at least
one gas burner 40 and flame divider means 9 comprising a
micro-perforated sheet used as a semi-permeable element 90. It is
however clear that the following detailed description should be
understood as an example which does not restrict the much broader
inherent inventive concepts of the present invention. Likewise, it
is clear that the advantages of the present invention remain
unchanged if the micro-perforated sheet is replaced with a
semi-permeable membrane made of metal or metal alloy fibers or of a
ceramic or composite material.
The micro-perforated sheet may be substantially discoidal in shape
and essentially orthogonal to the axis of the gas burner 40.
Moreover, the holes obtained in the sheet may be through holes with
axes essentially parallel to the axis of the gas burner 40:
following the combustion of the air-gas mixture, this setup
originates a carpet flame, i.e. a flame exiting the gas burner 40
in a substantially orthogonal direction relative to the visible
surface 30 of the cooking top 1. According to this embodiment, the
cooking top 1 according to the present invention differs from any
prior-art household cooking top also because it produces a carpet
flame instead of a crown flame. A carpet flame generally provides a
higher yield than a crown flame, and also overcomes the latter's
typical drawback of causing low-O.sub.2 flames and/or blackening in
the cooking top area surrounding the gas burner 40, if the flame is
emitted at an insufficient height above the visible surface 30 of
the cooking top 1.
In the cooking top 1 according to the present invention, the flame
divider means 9 and/or the semi-permeable element 90 are located
essentially at the same level above the visible surface 30 of the
cooking top 1. Furthermore, the pot supporting means 6 may reach a
height being equal to or lower than 30 mm above the visible surface
30 of the cooking top 1, preferably a height comprised between 15
mm and 20 mm above the visible surface 30 of the cooking top 1,
which is significantly lower than the height of about 45/50 mm
above the cooking top reached by pot supports used in prior-art
cooking tops for domestic use with at least one gas burner. Thanks
to this configuration of the flame divider means 9 comprising the
previously described micro-perforated sheet, it is also possible to
obtain a considerable lowering of the gas burner 40, which is also
perfectly in agreement with the current design trends aiming at
obtaining simple geometries with lines being as essential and
harmonious as possible. The generation of a similar carpet flame
and a resulting similar lowering of the burner may also be obtained
by using, instead of a micro-perforated sheet, a semi-permeable
membrane made of metal or metal alloy fibers or made of a ceramic
or composite material.
The flame divider means 9 comprising the micro-perforated sheet in
particular, and the semi-permeable element 90 in general, may be
secured in different alternative ways: first the gas burner 40 is
secured to the cooking top 1, and then the flame divider means 9
are applied together with the micro-perforated sheet by removably
or irremovably securing said means to the cooking top 1; first the
flame divider means 9 are removably or irremovably secured to the
third means of the gas burner 40, and then the burner is secured to
the cooking top or the flame divider means 9 are obtained in one
piece with another burner component, e.g. with the burner cup 20
appropriately shaped to comprise also an upper surface adapted to
be used as a semi-permeable element 90 (e.g. adapted to be
subjected to a micro-perforation treatment).
If a semi-permeable membrane is used, made of metal or metal alloy
fibers or of a ceramic or composite material, the requirement of
securing the membrane to the cooking top 1 may go side by side with
the need of giving adequate strength to the membrane. In such a
case, it is possible to shape the burner cup 20 to comprise
supporting means in its top area, on which the membrane is laid
before being secured. By way of example, said supporting means may
consist of profiles extending on the inner surface of the burner
cup 20 in a substantially radial direction, or of a grate connected
to the burner cup 20 and lying in a plane essentially orthogonal to
the axis of the gas burner 40.
According to an embodiment of the present invention, the
semi-permeable element 90 has a substantially annular shape, which
is considered to be particularly advantageous for at least one of
the two following reasons: secondary air is drawn with more
difficulty in the central area than in the peripheral area, so that
in the central area of the semi-permeable element 90 the combustion
of the air-gas mixture may be imperfect, thus generating unburnt
products (whose presence is indicated by so-called "yellow tips" on
flame ends) and generating a flame in the peripheral area of the
semi-permeable element 90 means producing an extended flame which
provides adequate heat distribution in the area above the gas
burner 40 during the food cooking process.
If the semi-permeable element 90 consists of a micro-perforated
sheet, it is possible to provide a distribution of the holes on the
micro-perforated sheet according to which the holes are more
densely distributed in the peripheral area than in the central area
as shown in FIGS. 3c and 3d.
According to the embodiment of the invention illustrated in FIGS.
2A and 2B, the cooking top 1 also comprises at least one securing
device 8, adapted to connect the flame divider means 9 to the
cooking top 1 and/or to the gas burner 40. The flame divider means
9 comprise housing means adapted to house the securing device 8.
The flame divider means 9 are so shaped as to have a hole 80 in
their central area, preferably a circular hole whose axis
essentially coincides with the axis of the gas burner 40. It is
conceivable to exploit said central area of the flame divider means
9 to secure the flame divider means 9 to the cooking top 1 and/or
to the gas burner 40 and to provide easy access to the internal
components of the gas burner 40 for maintenance purposes. Said
central hole 80 acts as a housing for the securing device 8 which,
passing through it, is then secured by means of a removable
connection, such as a screw-nut connection, to suitable supporting
means 5A-5N comprised in the third means of the gas burner 40
(preferably made integral with the burner cup 20, e.g. through spot
welding). The securing device 8 is a removable device and is
therefore adapted to grant access to the inside of the gas burner
40 for maintaining the gas burner 40 and for allowing the flame
divider means 9 and/or the semi-permeable element 90 to be removed
easily.
Preferably, the securing device 8 comprises two parts: a first part
2 being substantially discoidal in shape and a second part 3 being
substantially tubular in shape. The first part 2 has a larger
diameter than the diameter of the central hole 80 of the flame
divider means 9, whereas the second part 3 has a smaller diameter
than the diameter of the central hole 80 and is fitted, on its side
surface or at least a portion thereof, with anchoring means adapted
to ensure a firm connection between the securing device 8 and the
supporting means 5A-5N comprised in the third means of the gas
burner 40. The flame divider means 9 are thus secured to the gas
burner 40 because a portion of said flame divider means 9, in
particular the portion surrounding the central hole 80, is
interposed between the first part 2 of the securing device 8 and
the supporting means 5A-5N in such a way as to prevent the air-gas
mixture from flowing out between the flame divider means 9 and the
securing device 8 as well as between the flame divider means 9 and
the visible surface 30 of the cooking top 1. Since the connection
between the securing device 8 and the supporting means 5A-5N is a
removable connection, embodiment of the present invention
illustrated in FIGS. 2A and 2B ensures access inside the gas burner
40 for maintenance operations such as the replacement of the
injector 11. Furthermore, the embodiment of the present invention
illustrated in FIGS. 2A and 2B allows to remove the flame divider
means 9 and/or the semi-permeable element 90 easily from the
respective installation places, e.g. in order to wash them in a
dishwasher, replace the flame divider means 9 and/or replace the
semi-permeable element 90, in the event that these parts have
suffered damage and are no longer operating properly.
It may be particularly useful to provide the securing device 8 with
flow diverter means 4, adapted to help the air-gas mixture exiting
the Venturi element 10 to reach the semi-permeable element 90: for
this purpose, the second part 3 of the securing device 8 may be
flared or have a decreasing section, reaching its minimum diameter
on its free end. Since the semi-permeable element 90, according to
the present invention, may also be run through by a small quantity
of liquids (which however must be such as not to prevent a
subsequent ignition of the gas burner 40 should the flame be
extinguished), the flame divider means 9, comprising the
semi-permeable element 90, may be advantageously associated with
means adapted to divert said liquids toward areas wherein they
cannot hinder the operation of the gas burner 40.
As diverter means 13, one may use die-cast or forged profiles made
of sheet-metal, brass, cast iron or steel, comprising holes adapted
to allow gaseous substances to flow through (to supply the
combustion of the gas burner 40) and having a diameter adapted to
prevent said flow from suffering high load losses (e.g. the
diameter of the holes of the diverter means may be about 500 /600
.mu.m).
It is apparent from the present description that the cooking top,
in particular the cooking top 1 comprising at least one gas burner
40, according to the present invention overcomes the inherent
drawbacks of most cooking tops comprising at least one gas burner
currently available on the market, since it is much easier to
clean. It is also apparent that the generation of a carpet flame by
the gas burner and the semi-permeable element 90 (micro-perforated
sheet, metal or metal alloy fibrous membrane, or ceramic or
composite membrane) as described offers the users of the cooking
top 1 according to the present invention all the advantages which
distinguish a carpet flame from a crown flame, as enunciated in the
present description. However, said generation of a carpet flame
must not be considered to be a fundamental element of the present
invention, since the inherent inventive concepts of the present
invention may also be used to generate a crown flame instead of a
carpet flame. For this purpose, the flame divider means 9 and/or
the semi-permeable element 90 (micro-perforated sheet, metal or
metal alloy fiber membrane, or ceramic or composite membrane) may
have a substantially hollow cylindrical shape instead of a
substantially discoidal shape and may be positioned on top of the
gas burner 40 so as to allow the combustion air-gas mixture to flow
out of the gas burner 40 in a substantially radial direction. In
this case, the flame divider means do not delimit the gas burner 40
on top and may therefore be associated with covering means adapted
to prevent the air-gas mixture from flowing out of the gas burner
40 axially and possibly also to make it easier for the air-gas
mixture to reach the semi-permeable element 90. The inherent
inventive concepts of the above description may also be used to
generate an inclined flame, i.e. a flame which, when exiting the
flame divider means 9 and/or the semi-permeable element 90, has a
propagation direction not being parallel to either the visible
surface 30 of the cooking top 1 (like a crown flame) or the axis of
the gas burner 40 (like a carpet flame).
A much innovative aspect of the present invention concerns the use
of extended combustion areas inside of cooking tops, in particular
for domestic use; said areas may, for example, be shaped as a
circle, an ellipse, a polygon, a circular crown (as in the example
of FIGS. 2A and 2B), an elliptic crown, or a polygonal crown. Such
a cooking top comprises at least one gas burner and respective
flame divider means having a (burning) gas outlet area, as in the
examples of FIGS. 2A and 2B, and comprising a micro-perforated
sheet, a fibrous membrane, or a porous membrane.
Said area may extend in a substantially horizontal direction (the
horizontal direction being the direction in which the cooking top
is adapted to be arranged), as in the example of FIG. 2A; if the
extension of said area were not horizontal, but inclined by an
angle of e.g. 30.degree. or 45.degree. or 60.degree. , the flame
divider means would visibly protrude from the covering element of
the cooking top (the visible surface 30 in the illustrated
example).
The flame divider means may be so provided as to produce a gaseous
flow in a substantially vertical direction (the horizontal
direction being the direction in which the cooking top is adapted
to be arranged), i.e. directly toward the flat bottom of a cooking
container.
A cooking top using the "combustion area" concept may be fitted
with one or several gas burners.
In the former case, the cooking top comprises just one burner and
respective flame divider means, and the combustion area may
substantially take up the entire cooking area of the cooking
top.
In the latter case, the cooking top comprises a plurality of
cooking points, preferably two to six cooking points, and a
corresponding plurality of burners and flame divider means having a
corresponding plurality of spaced gas outlet areas.
The present invention has been described with reference to a
particular embodiment example, but it is clear that many changes
may be made thereto by those skilled in the art without departing
from the scope defined by the annexed claims.
* * * * *